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 | | Usually the stress distribution is tensile in the core and compressive at the surface. |
 | | Since the outer layer has already solidified, the shrinkage of the inner layer is resisted by the solidified outer layer, thus leading to a tensile stress in the outer layer and compressive stress in the inner layer. |
 | | Although many effects contribute to the residual stresses during injection molding of polymers, e.g., packing pressure, viscoelastic relaxation, non-constant material properties, degree crystallinity, etc., its formation may be adequately modeled using a one-dimensional thermo-elastic treatment that assumes constant material properties. |
| www.me.umn.edu /~kstelson/research_sbp/sbp/zhang.html (1417 words) |
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